Fifth wheel devices include a plate which supports the forward bed plate of a trailer. A king pin is fixed to the trailer bed plate and extends into a center opening of the fifth wheel plate. Fifth wheels have included a pivotally mounted jaw to engage and hold the king pin. Usually the king pin includes a reduced diameter neck and an enlarged end and the fifth wheel jaw surrounds the neck of the king pin so as to prevent it being disengaged either vertically or horizontally. Normally the jaw closes and is locked on the king pin as the tractor and trailer are brought together. However, there is also a mechanism provided to unlock the jaw to permit release of a king pin and allow separation of tractor and trailer. That mechanism must, for safety reasons, be manually operated by a driver or assistant and must include safeguards so as to avoid accidental release. However, the mechanism is normally an integral part of the fifth wheel structure and may be reached only by a driver reaching and leaning between trailer and tractor tires where there is minimal room to manipulate the mechanism.
Heretofore the mechanism for unlocking a fifth wheel jaw has usually required imparting a vertical lift to an operating rod. Unfortunately, vertical movement is difficult in the cramped space between trailer bed and tractor tires; and there is an increased available payload incentive to reduce the vertical dimension of that space to a minimum since a shorter vertical distance between trailer bed and tractor frame allows for a larger permissible vertical dimension of the trailer forward cargo space. Thus there is an advantage to minimizing the vertical dimension of the fifth wheel apparatus and any space required for its proper operation.